Patent GB-838973-A (GB)
Title: Improvements in or relating to  cellulosic material
Inventor: BALSTON JOHN NOEL
IPC: C08B15/06
Filed: 1957-04-16
Abstract: Cellulosic material is impregnated with an aqueous solution of a phosphorus acid and a non-metallic basic nitrogen-containing compound, or with an aqueous solution of a compound formed from a phosphorus acid and a non-metallic basic nitrogen-containing compound, the aqueous solution containing a relative proportion of nitrogen to phosphorus of at least one atom of nitrogen per atom of phosphorus, the ratio by weight of the solution to cellulose being at least 1.5 to 1 and the ratio by weight of cellulose to phosphorus acid in the reaction mixture not exceeding 5 to 1, and the impregnated material is heated for at least 20 minutes at a temperature of 120-200 DEG  C. so that the final product contains at least 5.5% of combined phosphorus.  The cellulosic material is preferably cotton or wood cellulose in thread, web, sheet, pulp, floc or powder form or regenerated cellulose in filament, film, web, yarn, powder or sheet form.  Non-cellulosic material may be admixed with the cellulosic material, e.g. glass or plastic fibres.  Reaction between the cellulosic material and the aqueous impregnating solution may be facilitated by a pretreatment of the cellulosic material with, e.g., alkali. Specified phosphorus acids are orthoand meta-phosphoric acids and phosphorous acid.  Urea is specified as a non-metallic basic nitrogen compound and it may be used alone or in conjunction with guanyl urea sulphate, amino guanidine hydrogen carbonate, guanidine nitrate, phenyl biguanide, formamide, ammonium phosphate, ammonium dihydrogen phosphate or urea phosphate. Ammonium phosphate and urea phosphate are specified as suitable compounds of a phosphorus acid and a non-metallic basic nitrogen-containing compound.  In the Provisional Specification buiret, acetamide, formamide, guanidine, aminoguanidine, biguanidine, and guanyl urea are also specified as basic nitrogen-containing compounds and dimethylamine phosphate, propylamine phosphate, guanyl urea phosphate and aminoguanidine phosphate are specified as additional compounds of phosphorus acids and nitrogen-containing compounds, aqueous solutions of which may be employed in the process.  Preferably the cellulosic material is heated with an impregnating solution the pH of which is between 2 and 7, adjustment being effected by addition of, e.g., ammonium hydroxide to the solution.  The heating of the impregnated cellulosic material may be effected in a revolving perforated drum, on a travelling band, in a cyclone-type drier, by infra-red heating means or preferably in a well-ventilated oven in which a heated gas, e.g. air, nitrogen or a mixture containing ammonia, passes through or over the impregnated cellulosic material.  After the heat treatment the impregnated cellulosic material may be treated for the removal of water-soluble substances, e.g. removal of phosphates by washing, and dried, preferably by heating in an oven in the presence of ammonia, or by washing with alcohol followed by ether.  The washing step may be followed by a reaction step in which the cellulosic material is converted to the hydrogen or a preferred salt form, e.g. the sodium or calcium form, by commencing the washing procedure with water and changing to a dilute acid in salt solution.  Examples are given.